Helicopter blade pitch lock

ABSTRACT

A helicopter blade pitch lock in which the locking takes place in the pitch change servos which are connected to the swashplate so as to vary blade pitch. The locking occurs by locking the fixed and movable members of the servo to one another, thereby locking the blade in pitch.

United States Patent [191 Ferris et al.

HELICOPTER BLADE PITCH LOCK Inventors: Donald L. Ferris, Newtown; LuigiVacca, Milford, both of Conn.

[73] Assignee: United Aircraft Corporation,

Hartford, Conn.

[22] Filed: Feb. 18, 1972 [21] Appl. No.: 227,359

[52] US. Cl. 416/114, 416/143 [51] Int. Cl. B64c 27/50 [58] Field ofSearch [56] References Cited UNITED STATES PATENTS 2,755,870 7/1956Gerstenberger 416/114 2,861,640 11/1958 DuPont 416/114 [451 Oct. 9, 19732,957,527 10/1960 Gerstenberger 416/114 2,973,815 3/1961 Sznycer 416/1142,978,038 4/1961 Doman et a1... 416/114 3,002,569 10/1961 Doblhoff416/153 X 3,207,227 9/1965 Timewell 416/46 3,219,121 11/1965 Barden416/153 3,256,780 6/1966 Riley et a1 416/114 X Primary Examiner-EveretteA. Powell, Jr. Att0rneyVernon F. Hauschild [5 7 ABSTRACT A helicopterblade pitch lock in which the locking takes place in the pitch changeservos which are connected to the swashplate so as to vary blade pitch.The locking occurs by locking the fixed and movable members of the servoto one another, thereby locking the blade in pitch.

6 Claims, 7 Drawing Figures PAIENTED HH 3776 saw 10F 5 4.229

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' PAIENTED 9 I975 SHEET 2 BF 5 FIG.4

PATENTEU GET 9 I975 SHEET 3 OF 5 IHR PATENTED BET 1 3 SHEET U [1F 5PATENTED URI 9 I573 SHEETSBFS FIC5-7 ing with respect to axis 16 so asto vary blade pitch cyclically. A plurality of servo assemblies 40 arepositioned circumferentially about swashplate assembly 30 and preferablyconsist of a piston member 42 having a piston rod 44 projectingtherefrom mounted for reciprocation along the axis 45 of cylinder orhousing 46. Cylinder or housing 46 is pivotally connected totransmission housing to be supported in pivotal but otherwise fixedrelationship therefrom. Accordingly, reciprocation of piston 42 withinpower piston-cylinder 46 causes motion of swashplate assembly and hencevaries the pitch of blades 12.

Referring to FIGS. 2 and 3 we see a first embodiment of the invention.Stationary swashplate member 32 is pivotally connected at pivotjoint 50to servo piston rod 44, which projects from servo housing or cylinder 46to reciprocate along cylinder and piston axis 45. The opposite end ofcylinder housing 46 is pivotally connected, as best shown in FIG. 1, totransmission housing 20 at pivot point 52. Piston rod 44 has lug member54 projecting therefrom and lug 54 includes aperture 56. Cylinderhousing 46 has cover member 58 attached thereto by any convenientconnecting means, such as bolt member 60, and spaced lugs 62 and 64project therefrom and include aligned apertures 66 and 68 which areadapted to align with aperture 56 of piston lug 54 so as to receivepitch lock pin 70 therethrough to lock the movable piston portion 42-44of servo to the stationary housing portion 46 thereof and therebylocking blades 12 in a fixed pitch condition for any purpose, such asblade folding.

Pitch lock pin 70 is actuated by power pistoncylinder unit 72 and isintegrally or otherwise conventionally connected to piston 74 thereof,which piston reciprocates along axis 76 of cylinder or housing 78. Powerservo 72 can be actuated in any convenient fashion, such aspneumatically or hydraulically, and is supported from lug 64 byconventional bolt mechanisms 80. Apertures 56, 66 and 68 preferablyinclude sleeve or bearing members 82, 84 and 86, as best shown in FIG.3. Locking pin 70 is forced into its locked position, shown in FIG. 3,by the introduction of motive fluid into chamber 88, and is retracted toits pitch unlock position by the introduction of motive fluid intochamber 90.

Follower arm 92 is pivotally connected to piston rod 44 at pivot point94 and is pivotally connected at its opposite end (not shown) to anyconvenient grounding mechanism, such as transmission housing 20, andincludes one or more slip joints 96 somewhere in its length to permitpiston 42 and piston rod 44 to reciprocate with respect to cylinderhousing 46 but to prevent rotation therebetween so that lug 54 willremain in alignment with lugs 62 and 64 and so that apertures 66, 56 and68 can be brought into alignment by reciprocation of piston 42 for bladepitch locking purposes when desired.

Preferably, as best shown in FIG. 2, the blade pitch is locked in thelow collective pitch range of servo 40 as demonstrated by gap 98 in FIG.2. Gap 98 is a definition of the additional travel of the servosnecessary to reach a low cyclic condition, which is past or beyond thepitch lock plane established for folding.

It is important to note that while a single power piston-cylinderassembly or servo 40 is shown in FIGS. 1 and 2, there are actuallypreferably three such servo assemblies positioned circumferentiallyabout stationary swashplate 32 to thereby establish the plane of theswashplate and the tip path plane of the blades.

A second embodiment of the invention is shown in FIGS. 4-7, to whichreference will now be made. Cylinder or housing 46 is again pivotallyconnected at pivot points 50 and 52 between the swashplate stationarymember 32 and a solid fixture, such as transmission housing 20. Piston42 and piston rod 44 reciprocate therewithin about cylinder and pistonaxis 45, so that the cylinder 46 is the servo stationary part and thepiston-piston rod 4244 is the servo movable part. The correspondingparts depicted in the FIGS. 4-7 modification will carry correspondingreference numerals to their counterparts in the FIG. 1 and 2embodiments. Housing 46 carries cylindrical sleeve 100 projectingtherefrom concentrically about axis 45 and piston rod 44 carriescylindrical sleeve 102 concentrically about axis 45 in overlappingrelationship to sleeve 100. Accordingly, as piston 42 is caused toreciprocate within cylinder 46 by the selective introduction of motivefluid into chambers 104 and 106 on opposite sides thereof, sleeves 100and 102 are caused to move relative to one another along axis 45 andswashplate assembly 30 is caused to correspondingly reciprocate so as tochange the pitch of the blades 12.

Seal or boot member 108 serves to prevent foreign matter from cloggingand creating friction in the surfaces between sleeves 100 and 102 andapertures 110 permits any contamination or condensation to be ejectedtherethrough.

As best shown in FIG. 5, sleeve 100 has substantially diametricallyopposed apertures 114 and 116 therein and sleeve 102 has substantiallydiametrically opposed apertures 118 and 120 therein. Apertures 114 and118 align, as do apertures 120 and l 16 so as to receive pitch lock pins70A and 70B. Lock pins 70A and 70B are integrally attached to pistons74A and 748, which reciprocate along axes 76A and 76B of cylinders 78Aand 78B of power servos 72A and 72B.

It is important to note that since apertures 114-120 are equidistant onopposites of axis 45, and therefore mates with lock pins 70A and 70Bequidistant on opposite sides of axis 45, cancelling bending moments areestablished in the servos 40 by this pitch lock mechanism.

Lock pins 70A and 70B are caused to reciprocate by the selectiveintroduction of motive fluid, such as hydraulic fluid, into the chamberson the opposite side of pistons 74A and 748 through conduits 130, 132,134 and 136, respectively.

Since it is important to have blades 12 remain in their pitched-lockedposition during periods of time when such condition is desired, pitchlock plunger is provided for each pitch lock pin 70A and 70B as bestshown in FIG. 6. FIG. 6 shows single pitch lock pin 70A, but it shouldbe borne in mind that FIG. 6 is equally applicable to the mechanism usedfor pitch lock pin 70B, which is preferably identical in all respects tothat shown in FIG. 6. Pitch lock-lock plunger 140 is received in annulargroove 142 of pitch lock pin 70A and serves to retain the pitch lock pin70A in the pitch locked condition shown in FIG. 5. Pitch lock-lockplunger 140 is hydraulically actuated by servo pistoncylinder mechanism144, which includes piston member 146 reciprocating within cylindermember 148. Pitch lock-lock plunger 140 can by hydraulically retractedby causing piston 146 to move rightwardly HELICOPTER BLADE PITCH LOCKCROSS-REFERENCES TO RELATED APPLICATIONS A Patent Application, Ser. No.227,395 entitled Helicopter Blade Pitch Lock in the names of GeorgeKudasch and Karl H. Wallischeck was tiled on Feb. 18, I972 herewith andclaims some of the subject matter shown and described herein.

BACKGROUND OF THE INVENTION l. Field of Invention This invention relatesto pitch locks for helicopter blades and more particularly for pitchlocks which perform the pitch lock function by locking the movableportion of the pitch change servo to the fixed portion of the pitchchange servo.

2. Description of the Prior Art It is known to be desirable to lockhelicopter blades against pitch change motion during operation, such asblade folding operation, to precisely position blades relative tospecific aircraft envelope requirements. Pitch locking also serves tokeep aerodynamic and blade weight shifting loads off the pitch changeservo mechanism, such as the hydraulic piston, upon which such loadswould be imposed if the blades were not locked in pitch.

It is conventional in the prior art, such as in U.S. Pats. Nos.3,438,446 or 3,369,61 l, to perform the pitch locking function bylocking the blade sleeve to the blade spindle. This requires a pitchlock for each blade and a total of six pitch locks when there are sixblades. It is known geometrically that any three points establish aplane. This holds true when establishing a pitch plane for all theblades in folding. The use of six pitch locks in the prior art, or anynumber of pitch locks over three, presents the problem of having tofinely tune the number of pitch locks over three into the plane of thethree established as the pitch lock plane to insure proper foldingoperation. This fine tuning of the extra pitch locks above three isconventionally done by manual adjustment which is time consuming anddifficult to accomplish. In addition, jamming, fretting and galling ofthe pitch locks has been encountered as a result of the fine tuningbecoming untuned. This produces a system with less reliability. Sincethe pitch change servos, of which there are three in a helicopter rotorsystem, are used to establish different pitch planes for the blades, itis convenient to attach the pitch lock system to these servos. Inaddition, the pitch plane required for blade folding must fall withinthe total pitch change range of the servos.

SUMMARY OF THE INVENTION A primary object of the present invention is toprovide an improved helicopter blade pitch lock mechanism in which themovable portion of the pitch change servo is connected or locked to thefixed portion of the pitch change servo, thereby locking the blades inpitch.

In accordance with the present invention, since there are but threepitch change servos in a conventional he- Iicopter rotor, the number ofpitch locks is reduced, thereby reducing the complexity and weightrequired by the pitch lock system.

A further feature of the present invention is the removing of the pitchlocks from the rotor head per se, thereby reducing rotor head drag,permitting a smaller rotor head package and eliminating the need forhydraulic slip rings between movable and stationary parts of thehelicopter for pitch lock actuation. However, hydraulic slip rings arestill needed for blade folding pin pullers.

In accordance with a further feature of the present invention, theimproved pitch lock locks the feathering axis of the blade at a selectedangle with respect to the plane of the rotor and this locking takesplace in a low collective pitch setting so that blades in their fullyfolded position present the least resistance to wind loads from anydirection.

A further feature of this invention is the freedom of the servos toactuate through the pitch lock plane to their fullest cyclic andcollective pitch ranges without interference of the pitch lockingmechanisms.

In accordance with a further aspect of the present invention, the entirepitch lock mechanism and its hydraulic actuating system are located on astationary, as opposed to a rotary portion of the helicopter.

In accordance with the present invention, the overall weight, complexityand reliability of the pitch lock system is improved.

Other objects and advantages of the present invention may be seen byreferring to the following description and claims, read in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial side view of ahelicopter rotor illustrating the environment of the invention.

FIG. 2 is an enlarged side view of a first embodiment of the pitch locksystem.

FIG. 3 is a view taken along line 3-3 of FIG. 2.

FIG. 4 is a side view of a second embodiment of the invention, partiallybroken away, to show the details of the pitch lock.

FIG. 5 is a partial cross-sectional showing taken along line 5-5 of FIG.4.

FIG. 6 is a cross-sectional showing, partly broken away, to show thelock-in and lock out members of one of the two pitch locking pins.

FIG. 7 is a schematic representation of the pitch lock actuating andsequencing system.

DESCRIPTION "OF THE PREFERRED I EMBODIMENT Referring to FIG. 1 we seehelicopter rotor 10 which comprises a plurality of blades 12 equallyspaced circumferentially about and supported from hub I4 so as to rotatetherewith in lift generating fashion about axis of rotation 16. Hub I4is supported from support sleeve 18 which may or may not be part oftransmission housing 20. Engine 22, which may be of any conventionaltype, serves to drive rotor 10 about axis 16 through transmission 24 soas to properly reduce engine speed to desired rotor speed. Each ofblades 12 is mounted from hub 14 so as to be rotatable about featheringaxis '26 so as to vary pitch. Pitch arm orhorn 28 projects from eachblade 12 and is connected to swashplate assembly 30 by a pitch changecontrol rod 31. Swashplate assembly 30 includes fixed swashplate member32 and rotatable swashplate member 34 connected through bearing system36. Swashplate assembly 30 is mounted from support sleeve 18 throughspherical ball 38 such that it is capable of reciprocation along axis 16to vary blade pitch collectively and so that it is capable of tiltwithincylinder 148 as shown in FIG. 6, thereby permitting the lock pin 70A tobe retracted by the action of servo 72A. Since it is equally desirableto have the pitch locks locked in their withdrawn or non-lockedpositions during periods when blade pitch locking is undesirable, apitch lock-unlock plunger 150 is provided for this purpose. As shown inFIG. 6, pitch lock-unlock plunger 150 is in its withdrawn condition byabutting the solid outer wall of lock pin 70A, despite the fact thatplungers 140 and 150 are bias toward axis 45 by spring members 152 and154. When pin 70A is withdrawn from engagement with aperture 118,plunger 150 is hydraulically actuated to its inboard position closestaxis 45 so as to physically prevent pitch lock 70A from returning to itsFIG. 5 locked position.

It will therefore be seen that the two pitch locks 70A and 70B are bothlocked in their pitch lock positions shown in FIG. 5 duringblade pitchlocked operation and locked out of their pitch lo ck positions duringblade pitch unlocked locked operation. Identical mechanism is used foreach pitch lock 70A and 70B of the type shown in FIG. 6.

The FIG. 4-7 modification includes hydraulic sequencing mechanism shownin FIG. 7 which serves the function of sequentially unlocking a lockedpitch lock for withdrawal, withdrawing the pitch lock and then lockingthe withdrawn pitch lock out of engagement and, conversely, sequentiallyunlocking a withdrawn pitch lock for engagement, actuating the pitchlock into engagement, and locking the pitch lock in pitch lockengagement. In this connection, it is important to note in FIG. 4 thatpiston sleeve member 102 includes projection 160 which aligns withproximity switch 162 of the FIG. 7 system when sleeves 100 and 102 areso positioned that apertures 114-120 are in alignment as shown in FIG.5. In addition, proximity switches 164 and 166 are positioned to be inalignment with projections 168 and 170 of pitch lock-lock plunger 140and pitch lock-unlock plunger 150, respectively, and these proximityswitches 162-166 provide signals to the pilot or operator to tell him ofthe position of piston 42 and plungers 140 and 150 at all times.

Referring to FIG. 7, we see a schematic of the sequencing and controlsystem for our pitch lock mechanisms and these pitch locks are shown intheir FIG. 5 locked positions. The sequence of operation which broughtthe pitch locks 70A and 708 into their locked position shown in FIGS. 5and 7 is that the pilot utilized conventional control mechanism toselectively position servo pistons 42 in servo housings 46 so as tobring apertures 114-120 into alignment, and therefore lug 160 intoalignment with proximity switch 162. Pilot must select fold mode tobring pump 208 to conduit 210 through valve 209. Proximity switch 162transmits an electrical signal through line 200 to shutoff valve 202 soas to cause the solenoid portion 204 thereof to move plunger 206 to theright. With plunger 206 to its far right position, hydraulic actuatingfluid from pump 208 is passed through selector valve 209 to conduit 210and shutoff valve 202 through conduit 212, from which it branches intoconduits 214 and 216. Hydraulic fluid from conduit 212 which passesthrough conduit 216 enters chamber 226 of plunger 150A so as to powerplunger 150A to its retracted position. Conduit 214 then conductshydraulic fluid through plunger 150A and conduit 218 into chamber 220 ofservo 72A so as to power pitch lock pin 70A to its FIG. 7 lockedposition, and then provides hydraulic fluid through conduit 222 tochamber 224 of plunger 140A to power it to its FIG. 7 locked position,once lock pin A is in its FIG. 7 locked position.

It will accordingly be seen that the signals from proximity switch 162,which indicated that apertures 114-120 of sleeves of and 102 were inalignment provided the necessary signal to withdraw lock-out plunger150A, to actuate lock pin 70A to its locked position, and to actuatelock-in lock plunger A to its locked position. In similar fashion, fluidfrom conduit 212 passes through conduit 228 and performs the samefunction with respect to plungers B, 140B and lock pin 70B.

Still viewing FIG. 7, lets consider the situation in which the bladesare in the locked condition shown in FIG. 7 and the pilot wishes tounlock the blades to permit pitch change thereof for normal flightoperation or other operations.

When the blades are in their fully unfolded or operable position,proximity switches on the rotor head (not shown) actuate selector valve209 so as to cause actuating fluid from pump 208 to pass through conduit250, then through conduit 252 to withdraw plunger 1408. With plunger140B withdrawn to thereby release lock pin 708 in its locked position,hydraulic fluid then passes through conduit 254 to retract lock pin 70Bfrom its FIG. 7 locked position to its retracted position. With the lockpin 70B so retracted, the hydraulic fluid then passes through conduit256 to drive plunger 150B to its active or locked position, therebylocking lock pin 708 into its retracted position as plunger 150B engagesthe recess in lock pin 70B now shown in FIG. 7 as being engaged byplunger 140. At the same time that this hydraulic sequence is takingplace with respect to the unlocking, withdrawal and relocking of lockpin 70B, hydraulic fluid passing through conduit 258 performs the samefunction simultaneously with respect to plunger 140A, lock pin 72A andplunger 150A.

It will accordingly be seen that signals from the rotor serve to utilizethe mechanism shown in FIG. 7 to se quentially unlock the locked bladelooks from their locked positions shown in FIG. 7, withdraw the bladelocks to a retracted or withdrawn position, and lock the blade locks inthat retracted or withdrawn position.

We wish it to be understood that we do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

We claim:

1. A helicopter rotorhaving:

A. a plurality of blades mounted for rotation about an axis and forpitch change motion,

B. means to vary blade pitch including:

1. a swashplate assembly mounted to be movable relative to said bladesand connected thereto so that swashplate motion causes blade pitchchange,

2. means to move said swashplate assembly including at least one powercylinder-piston assembly connected to said swashplate assembly,

3. means to lock said piston to said cylinder to thereby prevent bladepitch change motion, and

4. wherein said cylinder is stationary and said piston is movabletherewithin and attached to a piston rod which is connected to saidswashplate as-' sembly, and wherein said last named means includes lugmembers projecting from said piston rod and from said cylinder andhaving alignable apertures therein, and further including lock pin meansinsertable into said apertures when so aligned to lock said piston withrespect to said cylinder and hence prevent blade pitch change motion.

2. A helicopter rotor according to claim 1 wherein said swashplateassembly is mounted for motion between a low and a high collective pitchposition and wherein said apertures align to receive said lock pin meanswhen the swashplate assembly is at a low pitch position.

3. A helicopter rotor according to claim 1 and including means toselectively insert said lock pin means into said aligned apertures tolock said cylinder and said piston together and to withdraw said lockpin means from said apertures to free said piston from motion withrespect to said cylinder.

4. A helicopter rotor according to claim 1 and including three powercylinder-piston assemblies connected to said swashplate assembly andpositioned circumferentially thereabout.

S. A helicopter rotor having:

A. a plurality of blades mounted'for rotation about an axis and forpitch change motion,

B. means to vary blade pitch including:

1. a swashplate assembly mounted to be movable relative to said bladesand connected thereto so that swashplate motion causes blade pitchchange,

2. a servo mechanism comprising stationary and movable parts and with atleast one movable part connected to said swashplate to cause swashplatemotion, and

3. locking means actuatable to interconnect at least one servo mechanismmovable part to at least one servo mechanism stationary part to therebyprevent blade pitch change and where 6. A helicopter rotor having: A. aplurality of blades mounted for rotation about an axis of rotation andfor pitch change motion about a feathering axis,

B. means to vary blade pitch including:

1. a swashplate assembly mounted to be movable relative to said blade,

2. means connecting said swashplate to each of said blades so thatswashplate motion causes each of said blades to change pitch by movingabout said feathering axis,

3. a servo mechanism comprising stationary and movable parts and with atleast one movable part connected to said swashplate to cause swashplatemotion,

4. means to support said servo mechanism,

5. locking means actuatable to interconnect at least one servo mechanismmovable part to at least one servo mechanism stationary part to therebyprevent blade pitch change, wherein said locking means includesalignable apertures in said one servo mechanism movable part and saidone servo mechanism stationary part, and a pin member actuatable toextend through said aligned apertures to lock said one movable part andsaid one stationary part. and

6. means to actuate said pin member.

1. A helicopter rotor having: A. a plurality of blades mounted forrotation about an axis and for pitch change motion, B. means to varyblade pitch including:
 1. a swashplate assembly mounted to be movablerelative to said blades and connected thereto so that swashplate motioncauses blade pitch change,
 2. means to move said swashplate assemblyincluding at least one power cylinder-piston assembly connected to saidswashplate assembly,
 3. means to lock said piston to said cylinder tothereby prevent blade pitch change motion, and
 4. wherein said cylinderis stationary and said piston is movable therewithin and attached to apiston rod which is connected to said swashplate assembly, and whereinsaid last named means includes lug members projecting from said pistonrod and from said cylinder and having alignable apertures therein, andfurther including lock pin means insertable into said apertures when soaligned to lock said piston with respect to said cylinder and henceprevent blade pitch change motion.
 2. means to move said swashplateassembly including at least one power cylinder-piston assembly connectedto said swashplate assembly,
 2. A helicopter rotor according to claim 1wherein said swashplate assembly is mounted for motion between a low anda high collective pitch position and wherein said apertures align toreceive said lock pin means when the swashplate assembly is at a lowpitch position.
 3. A helicopter rotor according to claim 1 and includingmeans to selectively insert said lock pin means into said alignedapertures to lock said cylinder and said piston together and to withdrawsaid lock pin means from said apertures to free said piston from motionwith respect to said cylinder.
 3. means to lock said piston to saidcylinder to thereby prevent blade pitch change motion, and
 4. whereinsaid cylinder is stationary and said piston is movable therewithin andattached to a piston rod which is connected to said swashplate assembly,and wherein said last named means includes lug members projecting fromsaid piston rod and from said cylinder and having alignable aperturestherein, and further including lock pin means insertable into saidapertures when so aligned to lock said piston with respect to saidcylinder and hence prevent blade pitch change motion.
 4. A helicopterrotor according to claim 1 and including three power cylinder-pistonassemblies connected to said swashplate assembly and positionedcircumferentially thereabout.